Isoprene and Rubber. Part 44. Viscosity Measurements of Squalene and Hydrosqualene Solutions

1936 ◽  
Vol 9 (4) ◽  
pp. 573-578
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Physical Properties ◽  
General Relation ◽  
Basic Structure ◽  
Degree Of Polymerization ◽  
Specific Viscosity ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Rubber Part

Abstract The physical properties of highly polymerized substances, which are composed of fiber molecules, depend on the lengths of the chains of these fiber molecules. Thus tensile strength, elasticity, tendency to swell in solvents, and above all viscosity, are dependent on the length of chain of the particular substance. Among the substances, the properties of which vary thus, are rubber, gutta-percha, and balata. Since the length of fiber molecules can vary within wide limits, such physical properties as those mentioned above show wide variations in the case of rubber, gutta-percha, and balata. This is evident for example by a comparison of the properties of unmasticated rubber, which consists of long fiber molecules of a degree of polymerization of 2000, with the properties of masticated rubber, the greatly dissociated molecules of which have a degree of polymerization of only 500. The determination of the length of the fiber molecules is therefore of great importance in the case of highly polymerized substances. It has already been proved in past experiments with members of a series of homologous polymers, i. e., of substances the macromolecules of which have the same basic structure and differ only in length, that the molecular weights can be determined from viscosity measurements. This determination is based on the fact that there is a general relation between the specific viscosity and the length of the dissolved molecules, which can be expressed by the formula:

Molecular Weight and Chain-Length of Natural and Synthetic Rubber

1934 ◽  
Vol 7 (1) ◽  
pp. 34-39 ◽  
Author(s):  
A. J. Wildschut
Keyword(s):  
Chain Length ◽  
Freezing Point ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Synthetic Rubber ◽  
The Subject ◽  
Molecular Substances ◽  
Very High

Abstract The determination of the chain-length of high molecular substances, as, e.g., rubber and gutta-percha, has lately been the subject of many investigations, though as yet the problem has not been definitely solved. The ordinary methods—measurements of the raising of the boiling point and of the depression of the freezing point—can be used only for molecular weights of some thousands, and there always remains a large gap between these compounds and the far greater natural ones. To bridge over this gap Staudinger has developed a supposition according to which it is possible to determine very high molecular weights by means of a viscosimetric method. This method depends on the known fact that for dilute solutions, in which the molecules do not hinder each other (so-called sol-solutions), the specific viscosity is proportional to the length of the molecule. For homologs we have:

Isoprene and Rubber. Part 20. The Colloidal Nature of Rubber, Gutta-Percha, and Balata

1930 ◽  
Vol 3 (4) ◽  
pp. 586-595
Author(s):  
H. Staudinger
Keyword(s):  
Molecular Weight ◽  
Characteristic Viscosity ◽  
Specific Viscosity ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Viscosity Increase ◽  
Preceding Work ◽  
Rubber Part

Abstract I. The Molecular Weight of Rubber, Gutta-Percha, and Balata In the preceding work the molecular weight of rubber and balata was calculated on the basis of relations between specific viscosity ηsp and molecular weight which are shown by semi-colloidal decomposition products, on the assumption that this relation is also true for eucolloids. The value ηr−1 was taken as the specific viscosity, i. e., the characteristic viscosity increase of a substance of definite concentration and known solvent. The expression “specific viscosity” has already been used by J. Duclaux. In viscosity investigations of nitrocellulose solutions he represents this by a constant K which is calculated from the relations of the change of viscosity at various concentrations derived by Arrhenius: Based on these constants, nitrocelluloses show different average molecular weights for the increase in viscosity, that is, this constant K is greater with high molecular products than with low. In the following, this constant represents not the specific viscosity, but the viscosity-concentration constant Kc; the earlier constant Km which, on the basis of the formula: expressed the relation between the specific viscosity and the molecular weight, is called the viscosity-molecular weight constant.

Isoprene and Rubber. Part 45. Viscosity Measurements of Solutions of Rubber and Hydrorubber in Various Solvents

1936 ◽  
Vol 9 (4) ◽  
pp. 579-584
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Carbon Tetrachloride ◽  
Chain Length ◽  
Homologous Series ◽  
Chlorinated Solvents ◽  
Cellulose Derivatives ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Rubber Part ◽  
Viscous Solutions ◽  
Chain Lengths

Abstract It has been observed many times that solutions of the same concentration of rubber in various solvents show marked differences in viscosity. For example, solutions of rubber in chlorinated solvents such as carbon tetrachloride have higher viscosities than do solutions of the same concentration in benzene or benzine. These differences in viscosity are attributable to the fact that the rubber molecules are solvated in different ways in the various solvents. It may be further assumed that in a particular homologous series of polymers, all members, i. e., substances of both high and low molecular weights, are solvated in the same solvent in the same way, for only in this way is it possible to believe that the specific viscosity of solutions of like concentration increases with increase in the chain length, as has been found to be true of cellulose derivatives. In the previous experiments with squalene and hydrosqualene (cf. preceding article), the constants necessary for calculating molecular weights and chain member indices n were determined. The constants for carbon tetrachloride are higher than those for benzene. In the case of squalene, therefore, as in the case of rubber, carbon tetrachloride gives more viscous solutions than does benzene. If, now, rubbers and hydrorubbers are solvated in the same way as squalene and hydrosqualene, then the same chain lengths of an homologous series of rubber polymers would be obtained by calculations using constants derived from the simple compounds of the chain member index, and from this the degrees of polymerization, are calculated by means of these constants in the formula:

Isoprene and Rubber. Part 34. Molecules or Micelles in a Rubber Solution

1932 ◽  
Vol 5 (3) ◽  
pp. 265-277
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Colloidal Solutions ◽  
Dilute Solutions ◽  
Pure Nitrogen ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Colloid Particles ◽  
Rubber Part ◽  
Complete Exclusion ◽  
The Individual ◽  
Viscous Solutions

Abstract Measurements of the Viscosity of Rubber Solutions In the literature may be found numerous measurements of the viscosity of rubber solutions, the object of which was to throw light on the nature of colloidal solutions and changes in these solutions by various operations. These investigations give no insight into the structure of colloid particles and the reason for changes in rubber solutions because they are based on false assumptions, particularly the assumption that rubber has a micellar structure. Often highly viscous solutions were studied, and though these appeared to be of special interest to the colloid chemist, they were unsuited for such investigations, for they are gel solutions in which the structure of the colloid particles is much more difficult to explain than is that in dilute solutions (sol solutions), where the molecules have freedom of movement and do not disturb one another. The earlier works also contain references to the sensitivity of rubber to oxygen, though no special precautions were ever taken in the measurements to exclude oxygen; in fact this was unnecessary as a rule, for crude rubber solutions are much more stable, because of anticatalysts present, than solutions of pure rubber in which these have been removed. Pure rubber was prepared by the method of Pummerer and Pahl and, as described in the following work, was separated by fractional extraction into portions of different average molecular weights. Viscosity measurements of the individual fractions were then carried out under various conditions. The study of the rubber solution, like that of the balata solution, must be carried out with complete exclusion of air, and the solvent (tetralin or benzene) must be distilled in an atmosphere of pure nitrogen and be freed of oxygen. The filtration of the rubber solution, the filling of the viscosimeter, as well as the measurements themselves, are likewise made in an atmosphere of pure nitrogen. Measurements were taken in the Ubbelohde viscosimeter at different pressures, as a rule at 10.30 and 60 cm. mercury pressure. Very dilute solutions were also measured in the Ostwald viscosimeter, since the deviations from the Hagen-Poiseuille law are of no great importance at low concentration. Finally, it should be mentioned that these special precautions during the viscosity measurements, above all the careful exclusion of air, are necessary only in the case of rubber, not with the saturated hydrocarbons, polystyrene, and hydrorubber.

Determination of Degree of Polymerization of Cellulose in Ligneous Papers

1996 ◽  
Vol 462 ◽  
Author(s):  
E. Kaminska
Keyword(s):  
Strong Evidence ◽  
Degree Of Polymerization ◽  
Viscosity Measurements ◽  
The Past ◽  
Detailed Procedure

ABSTRACTIn the past, many attempts have been made to determine the degree of polymerization (DP) of cellulose in ligneous pulps or papers. Frequently, the methods employed caused severe depolymerization of the cellulose.The present paper provides a detailed procedure of DP determination of cellulose for both lignin-free and ligneous papers. The proposed method is based on viscosity measurements of cadoxen solutions of cellulose. Prior to dissolution in cadoxen, ligneous samples are partially delignified by a modified chlorite method, under conditions preventing any substantial depolymerization of cellulose. Results of preliminary experiments carried out on groundwood newsprint papers provide strong evidence of reliability of DP values so determined.

Determination of the Molecular Weights and the Structures of Rubber, Gutta-Percha and Balata. Communication No. 258 on Macromolecular Compounds. Communication No. 49 on Isoprene and Rubber

1942 ◽  
Vol 15 (3) ◽  
pp. 473-522
Author(s):  
H. Staudinger ◽  
Kl Fischer
Keyword(s):  
Small Molecules ◽  
Colloidal Particles ◽  
High Viscosity ◽  
Molecular State ◽  
Colloidal Solutions ◽  
Great Tendency ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Long Time

Abstract The method used to determine the constitutions of rubber, gutta-percha and balata is essentially the same as that used for organic substances of low molecular weights, i.e., the substance is dissolved in a solvent, and the size and character of the particles in solution are determined. For a long time the nature of colloidal solutions of these hydrocarbons was in dispute. Up to twenty years ago, it was commonly assumed that the molecules of these hydrocarbons are relatively small, and that their colloidal particles are formed by the assemblage of small molecules into micelles through the agency of secondary forces. It seemed to Pummerer, Nielsen and Gündel that in certain solvents, such as camphor and menthol, rubber is dissolved in a low-molecular state. Subsequently, however, this observation was proved to be incorrect. According to the opinion of Meyer and Mark, colloidal particles of rubber are composed of relatively long primary-valence chains, which contain from 75–150 isoprene residues. These chains are, in turn, assembled into micelles by “micellar forces.” The authors explain this in the following way: “The high viscosity of rubber solutions, e.g., in benzene, would lead one to conclude that very large, highly solvated micelles are present in these solvents.” At the time, this hypothesis seemed to explain quite satisfactorily the nature of rubber and its solutions, for the great tendency of these solutions to undergo certain changes on standing, which are manifest by an increase or decrease in viscosity, is readily comprehensible on this basis.

The Structure of Gutta-Percha Based on Studies with Electron Rays

1934 ◽  
Vol 7 (4) ◽  
pp. 603-607 ◽  
Author(s):  
G. Bruni ◽  
G. Natta
Keyword(s):  
Organic Compounds ◽  
Structural Investigations ◽  
X Ray ◽  
Molecular Weights ◽  
Vegetable Fibers ◽  
Gutta Percha ◽  
Natural Organic Compounds ◽  
Ray Methods ◽  
Identity Period

Abstract Among the natural organic compounds with high molecular weights which have been the object of roentgenographic investigations with a view to determining their intimate constitution, rubber and other hydrocarbons of similar constitution such as gutta-percha and balata have been extensively studied in recent years. The results obtained with these substances by x-ray methods have however not been so complete and reliable as in the case of other products with high molecular weights, such as cellulose, found in nature in ramie and in certain vegetable fibers in forms which are particularly well oriented, which is of enormous advantage in structural investigations. Nevertheless, the roentgenographic results on rubber are of the greatest interest because from them it is possible to show that the molecules of rubber are oriented when the rubber is stretched or frozen, so that it can be proved that under these special conditions it has a sort of crystalline structure which is characterized by definite identity periods. The determination of the identity period in the direction of the fibers, which is 8.1 A. U., is particularly reliable.

Transmission Electron Microscopy of Protein Macromolecules

1971 ◽  
Vol 29 ◽  
pp. 424-425
Author(s):  
Henry S. Slayter
Keyword(s):  
Biological Systems ◽  
Metal Vapor ◽  
Resolving Power ◽  
Electron Microscopic ◽  
Chemical Methods ◽  
Molecular Weights ◽  
The Past ◽  
Physical Chemical ◽  
Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

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